Tax accounting is based on the commercial accounting but with some special rules applicable. That being so, from the income obtained under commercial account, the following changes have to be made:
- Exempted and excluded income must be subtracted from the income base.
- Income taxed under special regimes must be also subtracted.
- Non-deductible expenses must be added to the income base.
- Other deductions different from expenses established by law, have to be subtracted from the tax base.
- The income resulting from the abovementioned operations will be the one subject to tax.